// Rust 没有继承 (inheritance) 机制，但可以通过 trait 和 supertrait 来实现类似的功能。
trait Person {
    fn name(&self) -> String;
}

// Person is a supertrait of Student.
// Implementing Student requires you to also impl Person.
// 这个是super的语法
trait Student: Person {
    fn university(&self) -> String;
}

trait Programmer {
    fn fav_language(&self) -> String;
}

// CompSciStudent (computer science student) is a subtrait of both Programmer 
// and Student. Implementing CompSciStudent requires you to impl both supertraits.
// 实现多个trait的语法
trait CompSciStudent: Programmer + Student {
    fn git_username(&self) -> String;
}

fn comp_sci_student_greeting(student: &dyn CompSciStudent) -> String {
    format!(
        "My name is {} and I attend {}. My favorite language is {}. My Git username is {}",
        student.name(),
        student.university(),
        student.fav_language(),
        student.git_username()
    )
}

fn main() {}